The present invention is directed to a device for delivery of medicament, and in particular to a single use disposable jet injector.
A wide variety of needle free injectors are known in the art. Examples of such injectors include those described in U.S. Pat. No. 5,599,302 issued to Lilley et al., U.S. Pat. No. 5,062,830 to Dunlap, and U.S. Pat. No. 4,790,824 to Morrow et al. In general, these and similar injectors administer medication as a fine, high velocity jet delivered under sufficient pressure to enable the jet to pass through the skin.
Although these injectors are quite successful from a technical point-of-view in achieving the desired delivery of medicament, most commercially available needle free injectors have practical limitations. For example, the use of a gas to power the jet injection, in the form of a gas spring or otherwise, has been problematic because of the potential for gas leakage with injector storage time and temperature sensitivity of the gas pressure. U.S. Pat. No. 4,913,699 discloses a gas powered disposable injector that uses carbon dioxide (CO2) and depends on the CO2 boiling off in a chamber and pressurizing a chamber that causes the plunger to move. U.S. Pat. No. 4,646,884 discloses an extended life gas spring that compensates for inherent leakage by being charged with gas and liquid such that as the gas leaks out, the liquid is converted to the gas phase. This is a reciprocal gas spring and the usage anticipates a gas spring in continuous service and is not a disposable device.
Another limitation of the prior art is the inability to use some needle free injectors with standard medicament cartridges, i.e. a cylindrical chamber, typically made of glass, having a first end with a seal penetrable by a needle to draw medicament out of the cartridge and a second end with a movable stopper. U.S. Pat. No. 5,891,086 discloses a needle-less injector in which one embodiment works with a sealed cartridge. As the nozzle is placed on one end of the cartridge, a piercing tube breaks the seal. As a result, the medicament in the cartridge is exposed to the nozzle until the injection is made. U.S. Pat. No. 6,132,395 does disclose a needle free injector that can be used with a glass cartridge. However, like the ""086 patent, the medicament is exposed to the environment prior to initiation of the injection, thereby potentially compromising the sterility of the medicament.
Thus, a need exists for an improved single use disposable jet injector.
The present invention relates to a jet injector comprising a cartridge assembly for holding medicament and a power pack assembly for providing energy to eject the medicament from the cartridge assembly with sufficient pressure for jet injection. The cartridge assembly includes a chamber (or tube with a lumen) for holding the medicament therein, an orifice at the proximal end of the cartridge assembly, a stopper at the proximal end of the chamber, and a plunger at the distal end of the chamber and movable toward the stopper to expel medicament out of the chamber through the orifice. The power pack assembly includes a housing having a proximal end operatively coupled with the distal end of the cartridge assembly, a trigger, and an energy source operatively associated with the trigger so that movement of the trigger activates the energy source to move the plunger toward the stopper to expel medicament from the chamber.
In an exemplary embodiment, the energy source is a gas spring containing a charging material existing in liquid and gaseous phase equilibrium within the gas spring to maintain a substantially constant pressure prior to activation. An example of a suitable charging material is carbon dioxide. The gas spring can have a wall with a coating to reduce gas permeability. Additionally, the injector can include a safety vent for releasing excess pressure and/or a temperature indicator for indicating that the jet injector has been exposed to temperatures outside of a set range.
In one embodiment, the cartridge assembly comprises an outer housing made of a polymer and an inner housing made of a glass. At least a portion of the plunger and stopper can be made of an elastomeric material. A needle, which can be beveled, is operatively associated with the proximal end of the cartridge assembly and has a piercing end extending toward the chamber. The stopper is movable within the chamber toward the piercing end of the needle and relative movement between the stopper and the needle causes the piercing end of the needle to pierce the stopper to create a fluid pathway for the medicament through the needle. Movement of the plunger toward the proximal end of the chamber compresses the medicament held between the plunger and the stopper so that the medicament is expelled through the fluid pathway. The movement of the plunger toward the proximal end of the chamber also compresses the medicament between the stopper and the plunger to move the stopper toward the proximal end of the cartridge assembly to allow the piercing end of the needle to pierce the stopper and create the fluid pathway for the medicament through the needle.
The stopper can have a frustroconical shape and the plunger can have a medicament contacting surface configured and dimensioned to mate with the frustroconical shape of the stopper to minimize volume of medicament remaining in the chamber after the injection is completed. In order to facilitate creation of the fluid pathway, the stopper can have a narrow cross-section where the needle penetrates the stopper. In other embodiments, the plunger comprises a front member having a recess and an substantially non-compressible insert received in the recess. Additionally, the plunger and/or stopper can include ridges formed around an outer periphery to provide a seal and create a sterile boundary between the medicament and an exterior of the cartridge assembly.
The power pack assembly can include a distal housing having a lumen containing the charging material and a proximal housing connectable with the distal housing and having an inner surface with a ledge for receiving locking tabs on the cartridge assembly to couple the cartridge assembly thereto. A portion of an exterior surface of the proximal housing has threads and a portion of a lumen wall has threads. The proximal housing threads mate with the lumen wall threads to connect the proximal and distal housings.
In an exemplary embodiment, a ram has a proximal end contacting the plunger and a distal end having a seal so that the gas spring is defined by the lumen wall and the seal. The ram has a recess and the inner surface of the proximal housing has a latch member insertable into the recess to thereby prevent the gas spring from moving the ram and the plunger toward the stopper. Movement of the trigger allows the latch member to bend away from the recess to thereby allow the gas spring to move the ram and the plunger toward the stopper. The trigger can include a tubular body substantially covering the cartridge assembly, a cap operatively associated with the proximal housing, and struts connecting the body and the cap.